The timing of the funding cut is a major own goal just days out from the referendum.

The decision by the State child and family agency, Tusla, is expected to be cited by 'No' campaigners as an effort to undermine the institution of marriage.

Bishop Denis Nulty, president of Accord Catholic marriage care service, confirmed Tusla wrote to the agency last week to inform them of the withdrawal of funding.

Bishop Nulty said he was "very disappointed" a decision had been taken to withdraw funding which would "certainly undermine a vital service provided to women and men preparing for marriage".

The Bishop said the Accord service received a letter from Tusla stating: "Following confirmation of Tusla's budget for 2015 by Minister (James) Reilly on 27 April... a decision has been made to withdraw funding for Marriage Preparation Courses from 2015 onwards."

Accord received €1.992m in funding from Tusla in 2014 and this year will receive just €1.6m.